1. Field of the invention
This invention relates to a torque variation absorbing device for use in a driving axle system.
2. Description of the Related Art
A conventional torque variation absorbing device is disclosed in the Japanese Utility Model Laid-Open No. 64-48448 published in 1989 without examination. In FIGS. 7 and 8 the torque variation absorbing device comprises a drive body 61 which is connected to a crank shaft (not shown in the FIGURES) of an engine of a vehicle and a driven body 62 on which a clutch mechanism (not shown in the FIGURES) is mounted. The drive body 61 includes a pair of drive plates 63 and a drive wheel 64 which is connected to the drive plates 63 with a plurality of pins 65. Furthermore the drive body 61 includes a hub 67 which is connected to one of the drive plates 63 with a plurality of screws 66.
The driven body 62 includes a flywheel 68 and a driven plate 70 which is connected to the flywheel 68 with a plurality of bolts 69. A plurality of damping mechanisms 76 are disposed between the drive plates 63. A bearing 71 is disposed between the driven plate 70 and the hub 67. Furthermore a friction member 72, a thrust plate 73 and a cone spring 74 constitute a hysteresis mechanism 75 disposed between the drive plate 63 and the driven plate 70.
Because the hysteresis mechanism 75 is composed of only one friction member formed of low hysteresis material which possesses a single stage, the hysteresis mechanism 75 can efficiently absorb torque variations when the torque variation absorbing device is subjected to a low torsional angle. However the hysteresis mechanism 75 fails to absorb the sympathetic vibrations when the torque variation absorbing device is subjected to a high torsional angle. Therefore a driver is conscious of the trangient surge by the operation of the accelerator of the vehicle.
On the other hand the hysteresis mechanism formed of high hysteresis material fails to absorb the variations when the torque variation absorbing device is subjected to the low torsional angle.